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package java.security.interfaces;

import java.security.*;

/**
 * An interface to an object capable of generating DSA key pairs.
 *
 * <p>The {@code initialize} methods may each be called any number
 * of times. If no {@code initialize} method is called on a
 * DSAKeyPairGenerator, the default is to generate 1024-bit keys, using
 * precomputed p, q and g parameters and an instance of SecureRandom as
 * the random bit source.
 *
 * <p>Users wishing to indicate DSA-specific parameters, and to generate a key
 * pair suitable for use with the DSA algorithm typically
 *
 * <ol>
 *
 * <li>Get a key pair generator for the DSA algorithm by calling the
 * KeyPairGenerator {@code getInstance} method with "DSA"
 * as its argument.
 *
 * <li>Initialize the generator by casting the result to a DSAKeyPairGenerator
 * and calling one of the
 * {@code initialize} methods from this DSAKeyPairGenerator interface.
 *
 * <li>Generate a key pair by calling the {@code generateKeyPair}
 * method from the KeyPairGenerator class.
 *
 * </ol>
 *
 * <p>Note: it is not always necessary to do do algorithm-specific
 * initialization for a DSA key pair generator. That is, it is not always
 * necessary to call an {@code initialize} method in this interface.
 * Algorithm-independent initialization using the {@code initialize} method
 * in the KeyPairGenerator
 * interface is all that is needed when you accept defaults for algorithm-specific
 * parameters.
 *
 * <p>Note: Some earlier implementations of this interface may not support
 * larger sizes of DSA parameters such as 2048 and 3072-bit.
 *
 * @see java.security.KeyPairGenerator
 */
public interface DSAKeyPairGenerator {

  /**
   * Initializes the key pair generator using the DSA family parameters
   * (p,q and g) and an optional SecureRandom bit source. If a
   * SecureRandom bit source is needed but not supplied, i.e. null, a
   * default SecureRandom instance will be used.
   *
   * @param params the parameters to use to generate the keys.
   * @param random the random bit source to use to generate key bits; can be null.
   * @throws InvalidParameterException if the {@code params} value is invalid, null, or
   * unsupported.
   */
  public void initialize(DSAParams params, SecureRandom random)
      throws InvalidParameterException;

  /**
   * Initializes the key pair generator for a given modulus length
   * (instead of parameters), and an optional SecureRandom bit source.
   * If a SecureRandom bit source is needed but not supplied, i.e.
   * null, a default SecureRandom instance will be used.
   *
   * <p>If {@code genParams} is true, this method generates new
   * p, q and g parameters. If it is false, the method uses precomputed
   * parameters for the modulus length requested. If there are no
   * precomputed parameters for that modulus length, an exception will be
   * thrown. It is guaranteed that there will always be
   * default parameters for modulus lengths of 512 and 1024 bits.
   *
   * @param modlen the modulus length in bits. Valid values are any multiple of 64 between 512 and
   * 1024, inclusive, 2048, and 3072.
   * @param random the random bit source to use to generate key bits; can be null.
   * @param genParams whether or not to generate new parameters for the modulus length requested.
   * @throws InvalidParameterException if {@code modlen} is invalid, or unsupported, or if {@code
   * genParams} is false and there are no precomputed parameters for the requested modulus length.
   */
  public void initialize(int modlen, boolean genParams, SecureRandom random)
      throws InvalidParameterException;
}
